Process and apparatus for producing an endless seamed belt

ABSTRACT

A novel method and apparatus for producing an endless flexible seamed belt using a punch and die is disclosed. The punch and die have patterned edges in the form of a puzzle cut pattern with extremely small nodes and kerfs. The cutting tolerances of the patterned edges make it necessary to fix the punch with respect to the die so that there is no misalignment of the punch and die between cutting operations. This is accomplished by resiliently fixing the punch to the die, rather than having the punch attached to the force generating assembly as in normal punch and die assemblies. Belt material is positioned between a stock gap between the punch and die and the force generating assembly is activated to provide the cutting force. Once the belt material is cut, the cutting force is removed and the force generating assembly returns to its retracted position. There are two cutting edges on the punch and die so that a first end of one belt and a second end of another belt are formed in a single cutting operation.

CROSS REFERENCE TO RELATED APPLICATIONS

Attention is hereby directed to U.S. patent application Ser. No.08/297,200) entitled “Puzzle Cut Seamed Belt”, now U.S. Pat. No.5,514,436, issued May 7, 1996; U.S. patent application Ser. No.08/297,158 entitled “Puzzle Cut Seamed Belt With Strength EnhancingStrip”, now continuing U.S. patent application Ser. No. 08/522,622,filed Aug. 31, 1995; U.S. patent application Ser. No. 08/297,201entitled “Puzzle Cut Seamed Belt With Bonding Between Adjacent SurfaceBy UV Cured Adhesive”, now U.S. Pat. No. 5,487,707, issued Jan. 30,1996; U.S. patent application Ser. No. 08/297,206 entitled “EndlessSeamed Belt with Low Thickness Differential Between the Seam and theRest of the Belt”, allowed, but not yet issued; and U.S. patentapplication Ser. No. 08/297,203 entitled “Puzzle Cut Seamed Belt withBonding Between Adjacent Surfaces”, all commonly assigned to theassignee of the present invention and filed on Aug. 29, 1994.

This invention relates generally to a process and apparatus forproducing an endless seamed belt, and more particularly concerns theconfiguration of the die press components used to cut a flexibleseamless belt with interlocking patterned ends.

Initially, belts were fabricated by taking two ends of a web materialand fastening them together by a variety of techniques such as sewing,wiring, stapling, providing adhesive joints, etc. While such joined orseamed belts are suitable for many applications, such as the delivery ofrotary motion from a source such as a motor, to implement a device suchas a saw blade, they are not as satisfactory in many of the moresophisticated applications of belt technology in common practice today.In the technology of the current day many applications of belts requiremuch more sophisticated qualities and utilities and in particular forsuch special applications as in electrostatographic and electrographicimaging apparatus and processes for use as photoreceptors, intermediatesheet and/or image transport devices, fusing members or transfix devicesit is ideal to provide a seamless belt whereby there is no seam in thebelt which mechanically interferes with any operation that the beltperforms or any operation that may be performed on the belt. While thisis ideal the manufacture of seamless belts requires rather sophisticatedmanufacturing processes which are expensive and are particularly moresophisticated, difficult and much more expensive for the larger belts.As a result, various attempts have been made to provide seamed beltswhich can be used in these processes. Previous attempts to manufactureseamed belts have largely relied on belts where the two ends of the beltmaterial have been lapped or overlapped to form the seam or have buttedagainst one another and then fastened mechanically by heat or othermeans of adhesion such as by the use of an adhesive or ultrasonicwelding.

The belts formed according to the typical butting technique whilesatisfactory for many purposes are limited in bonding, strength andflexibility because of the limited contact area formed by merely buttingthe two ends of the belt material. Furthermore, belts formed accordingto the butting or overlapping technique provide a bump or otherdiscontinuity in the belt surface leading to a height differentialbetween adjacent portions of the belt, of 0.010 inches or more dependingon the belt thickness, which leads to performance failure in manyapplications. For example, one of the most severe problems involvescleaning the imaging belt of residual toner after transfer of the tonerimage. Intimate contact between the belt and cleaning blade is required.With q bump, crack or other discontinuity in the belt the tuck of theblade is disturbed which allows toner to pass under the blade and not becleaned. Furthermore , seams having differential heights may whensubjected to repeated striking by cleaning blades cause theuntransferred, residual toner to be trapped in the irregular surface ofthe seam. Furthermore, photoreceptors which are repeatedly subjected tothis striking action tend to delaminate at the seam when the seam issubjected to constant battering by the cleaning blade. As a result, boththe cleaning life of the blade and the overall life of the photoreceptorcan be greatly diminished as well as degrading the copy quality. Inaddition, such irregularities in seam height provide vibrational noisein xerographic development which disturb the toner image on the belt anddegrades resolution and transfer of the toner image to the final copysheet. This is particularly prevalent in those applications requiringthe application of multiple color layers of liquid or dry developer on aphotoreceptor belt, which are subsequently transferred to a final copysheet. In these applications, it is desired to provide a seam heightdifferential between the seam and the unseamed adjacent portions lessthan 0.001 inch. In addition, the presence of the discontinuity in beltthickness reduces the flex life and continuity of strength of the beltwhich for prolonged use is desirably 80-90% that of the parent materialunseamed. In addition, the discontinuity or bump in such a belt mayresult in inaccurate image registration during development, inaccuratebelt tracking and overall deterioration of motion quality, as a resultof the translating vibrations.

An endless seamed belt can be formed with patterned interlocked ends,the pattern of the ends being formed by using a laser or a die to cutthe pattern and the patterned cut ends being brought together tointerlock to form a seam. In experiments the patterned seams were firstgenerated using a CO2 laser programmed to make various patterned nodesizes and spacings. The laser was an excellent tool for quickly changinggeometries and conditions, however it was a costly and timely processand an inappropriate process for manufacturing seams for large volumesof belts. A 1 inch length punch press die was designed to cut small beltseam samples for testing purposes. The die cut is much faster andcleaner than the laser cut and the die cut was determined to be thepreferred method to be used in the patterned seam belt manufacturingprocess. However, the size, approximately 0.5 mm, and spacings,approximately 25 microns, of the nodes of the pattern require veryaccurate cutting by a die and it was thought to be impossible for a dieto maintain such demanding tolerances for the width of an operationalbelt seam.

The following disclosures may be relevant to various aspects of thepresent invention:

U.S. Pat. No. 1,303,687 Inventor: C. Leffler Issued: May 13, 1919 U.S.Pat. No. 2,461,859 Inventor: A. J. Vasselli Issued: Feb. 15, 1949 U.S.Pat. No. 2,792,318 Inventor: H. P. Welch Issued: May 14, 1957 U.S. Pat.No. 4,878,985 Inventor: Thomsen et al. Issued: Nov. 7, 1989 U.S. Pat.No. 5,286,586 Inventor: Foley et al. Issued: Feb. 15, 1994 U.S. Pat. No.4,624,126 Inventor: Avila et al. Issued: Nov. 25, 1986

Some relevant portions of the foregoing disclosures may be brieflysummarized as follows:

U.S. Pat. No. 1,303,687 teaches forming a container from a body blankwith the ends dovetailed together and a covering sheet which extendsbeyond the end of the body and has its extending portion secured down,overlapping the dovetail joint to secure and finish the container. Informing the container, the body blank is wrapped around a formingmandrel of the desired shape and the two dovetail ends are interlocked.At the same time the extending ends of the covering sheet, which areprovided with adhesive, are stuck down overlapping the joint.

U.S. Pat. No. 2,461,859 teaches an endless flexible belt with apatterned dovetail joint. A single die cut may cut both ends of thepatterned dovetail joint at the same time. The ends of the belt are cutto form a male and female end with a plurality of spaced dovetailedtabs, the female end fitting into the male end and the dovetailed tabsinterlocking with each other. An adhesive may be used at the belt joint.

U.S. Pat. No. 2,792,318 discloses forming splice joints in fibrousmaterial, each joint being cut so that an interlocking tongue and groovepattern is formed. The tongues and grooves may be different shapes. Inthe finished product, the joints are oriented at a diagonal with respectto the sides. A coating material may be used to maintain the interfittedtongues and grooves, however, it is the interlocking connection of thetongues and grooves that provides the tensile strength of the joint.

U.S. Pat. Nos. 4,878,985 and 5,286,586 disclose fabricating thinflexible endless belts used in electrophotographic printing systems. Thepatents teach overlapping the ends of the belt and welding the endstogether to form an endless belt.

U.S. Pat. No. 4,624,126 teaches a hydraulic press with a cylinderarrangement for equalizing forces in the event of unequal loading of thepress.

All of the above references are herein incorporated by reference.

SUMMARY OF THE INVENTION

One aspect of the invention is drawn to an apparatus for producing anendless flexible seamed belt from belt material stock including a beltmaterial positioner which positions the belt material stock for cutting;a die assembly including a die with a first die cutting edge having afirst die pattern; a punch assembly including a punch with a first punchcutting edge having a first punch pattern that is complementary to thefirst die pattern; and a force generating assembly which generates acutting force in a cutting operation in which the punch and die cut thebelt material so that a first patterned end is formed on a first end ofthe belt and a second patterned end is formed on a second end of thebelt, wherein the first and second patterned ends of the belt are cut ina puzzle cut pattern with mutually mating elements which fit together toform a seam when joined mechanically to enable the endless flexibleseamed belt to essentially function as an endless belt having asubstantially uniform thickness.

Another aspect of the invention is drawn to a method of making anendless flexible seamed belt from belt material stock includingpositioning the belt material stock between a die assembly and a punchassembly, the die assembly including a die with a first die cutting edgehaving a first die pattern and the punch assembly including a punch witha first punch cutting edge having a first punch pattern that iscomplementary to the first die pattern; applying a cutting force from aforce generating assembly to a force receiving surface on the punchassembly so that the die and punch cut the belt material to form a firstpatterned end on a first end of the belt and a second patterned endformed on a second end of the belt; and removing the cutting force fromthe punch assembly, wherein the first and second patterned ends of thebelt are cut in a puzzle cut pattern with mutually mating elements whichfit together to form a seam when joined mechanically to enable theendless flexible seamed belt to essentially function as an endless belthaving a substantially uniform thickness.

In a manufacturing mode, it is desirable to have a fast and accuratemethod of forming the puzzle cut seam design. Using a die to cut theflexible belt material is much quicker than using a laser to form thepuzzle cut seam. The die cut is also cleaner than the laser cut due tothe fact that the laser melts the belt material, which is a particularproblem in a multi-layered belt. Having a clean puzzle cut seam is veryimportant when the belt is used in an electrophotagraphic machineenvironment due to the very small distances between theelectrophotagraphic process elements and the belt. A special die with atolerance of 0.0002 inch runout in a 60 inch linear plane was designedand fabricated to cut the small nodes and spacings of the puzzle cutseam. In order to maintain the close tolerances of the patterned cuttingedges of the die, a novel die press and method of using the die had tobe invented. The die is formed so that the back end of one belt isformed in the same punch as the front end of another belt. This resultsin a small area of waste material between the two ends, however the timeand energy saved in placing and cutting the two ends independently faroutweigh the cost of the waste material.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features of the present invention will become apparent as thefollowing description proceeds and upon reference to the drawings, inwhich:

FIG. 1 is an isometric representation of the flexible puzzle cut seamedbelt providing a mechanically invisible and substantially equivalentseam in performance to that of a seamless belt.

FIG. 2 is an enlarged view of a puzzle cut pattern used on both joiningends of the belt material to provide interlocking elements having a postportion 14 and a larger head portion 16.

FIG. 3 is illustrative of an alternative configuration wherein male 18,19 and female 21, 23 interlocking portions having curved mating elementsare used in the two ends of the belt material which are joined.

FIG. 4 is a further alternative embodiment wherein the interlockingelements 30, 32 form a dovetail pattern having curved mating elements.

FIG. 5 is an additional alternative embodiment wherein the interlockingrelationship between the puzzle cut pattern on both ends is formed froma plurality of finger joints 22, 26.

FIGS. 6A, 6B and 6C are three representations of the puzzle cutconfiguration which will be discussed hereinafter.

FIG. 7 is a greatly exaggerated in scale representation illustratingessentially no space between interlocking elements.

FIG. 8 is a greatly exaggerated in scale representation of the seam typegeometry, a very narrow kerf 20, that will be bonded by heat andpressure alone.

FIG. 9 is a greatly exaggerated representation of the belt seam 11 withthe kerf 20 filled with belt compatible material represented by crosshatching.

FIG. 10 is a front view of the die press used to form the puzzle cutbelt ends.

FIG. 11 is an exploded view of the cutting elements in the die press.

While the present invention will be described in connection with apreferred embodiment thereof, it will be understood that it is notintended to limit the invention to that embodiment. On the contrary, itis intended to cover all alternatives, modifications, and equivalents asmay be included within the spirit and scope of the invention as definedby the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

With continued reference to the Figures and additional reference to thefollowing description the invention will be described in greater detail.The seam formed according to the present invention is one of enhancedstrength, flexibility and mechanical life which is held together by thegeometric relationship between the ends of the belt material, which arefastened together by a puzzle cut, meaning that the two ends interlockwith one another in the manner of an ordinary puzzle and wherein theseam has voids or a kerf 20 between the surfaces of mutually matingelements, the opposite surfaces of the puzzle cut pattern being joinedtogether to enable the seamed flexible belt to essentially function asan endless belt. The joining of the opposite surfaces of the mutuallymating elements forming the seam may be either a physical joining,chemical joining or some combination of physical and chemical joining.The opposite surfaces of the puzzle cut pattern may alternatively bebound with an adhesive which is physically and chemically compatiblewith the belt material. Typically, this joining provides a bondingbetween the opposite surfaces of the mutual mating elements whichprovides an improved seam quality and smoothness with substantially nothickness differential between the seam and the adjacent portions of thebelt thereby providing enhanced imaging, registration and control asdiscussed above. In this regard, it should be noted that the lower thedifferential in height, the faster that the belt may travel. In anycase, the opposite surfaces of the puzzle cut pattern being joinedtogether are bound with sufficient physical integrity to enable theseamed flexible belt to essentially function as an endless belt. The twoends of the seamed belt may be joined by heating such as by welding,including ultrasonic welding, arc welding and impulse welding, whereintop and bottom elements similar to those that are used to seal plasticbags have two arms which apply pressure and then the elements areheated. In the case of thermoplastic belt materials the thermoplasticnodes may be deformed by heating and may flow into the voids to form orlink together and physically form the bond. As illustrated in FIG. 8 avery narrow kerf between thermoplastic ends of the belt may be filled bythe mere application of heat and pressure. This is like welding the twonodes together. This technique of course is not applicable to thermosetmaterials.

Alternatively the two ends of the belt having the puzzle cut pattern ateach end may be joined by a chemical reaction. This happens in theinstance where the belt material is a thermoplastic and upon heating thethermoplastic at least softens, if not melts, and flows to fill thevoids in the seam.

Another alternative is to apply an adhesive to the voids between themutually mating elements, and in particular, to the opposite surfaces ofthe puzzle cut pattern. With the use of an adhesive a much wider kerfmay be used than the very narrow kerf that may be used for bonding byheat and pressure only thermoplastic materials. This also permits theadhesive to wick into the void or kerf areas. In this regard, theviscosity of the adhesive is important since it's performance depends onit's ability to wick into the voids or the kerf 20 between adjacent cutpieces of the pattern. Accordingly, a relatively high viscosity adhesivewill not perform as satisfactorily as a low viscosity adhesive. Inaddition, the surface energy of the adhesive must be compatible with thematerial from which the belt is fabricated so that it adequately wetsand spreads in the belt seam. As previously described good adhesion isrequired to enable the performance requirements previously discussedwith regard to comparing it to the original material. If the belt ismade of a thermoplastic or thermoset material, i is quite convenient touse thermoplastic or thermoset adhesives which melt and flow at atemperature below that of the belt material but do not soften enough orflow during the belt's operation. The kerf 20, the distance betweenadjacent surfaces of the mutually mating elements of the belt ends canbe built into the belt ends by way of a mechanical die or it can bebuilt into by way of cutting with a laser pattern. If the belt materialis a thermoplastic, a thermoplastic or thermoset or otherwisecrosslinked adhesive may also be used and indeed may be based on thesame material that the belt is fabricated from. However, if the beltmaterial is thermosetting then a thermoplastic or thermoset adhesive maybe used to fill the voids between the opposite surfaces of the puzzlecut pattern. Typically, a hot melt adhesive may be used, which is onethat is solid at room temperature, however, when heated will flow.Typical thermoplastic hot melt adhesives include polyamides, urethanes,polyesters. Typical thermosetting materials include epoxies, polyimides,cyanoacrylates and urethanes. Following bonding, whether it be physical,chemical or by way of adhesive or any combination of the above, althoughit may not be necessary, it may be desirable to apply pressure toflatten the seam to make it as uniform as possible and control anythickness differential.

Referring to FIG. 1, it should be noted that the mechanical interlockingrelationship of the seam 11 is present in a two dimensional plane whenthe belt 10 is on a flat surface, whether it be horizontal or vertical.While the seam is illustrated in FIG. 1 as being perpendicular to thetwo parallel sides of the belt it will be understood that it may beangled or slanted with respect to the parallel sides. This enables anynoise generated in the system to be distributed more uniformly and theforces placed on each mating element or node to be reduced.

The endless flexible seamed belt may be made of any suitable material.Any suitable belt material may be employed. Typical materials include,photoreceptor materials which may be multilayered such as thosedescribed in U.S. Pat. No. 4,265,990, as well as a variety ofthermoplastic and thermosetting belt materials. Typical materialsinclude polyesters, polyurethanes, polyimides, polyvinyl chloride,polyolefins such as polyethylene and polypropylene and polyamides suchas nylon, polycarbonates, acrylics. In addition, elastomeric materialssuch as silicones, fluorocarbons such as Vitons E. I. DuPont™, EPDM andnitriles etc. For certain purposes, metallic; cloth and even paper maybe used. The belt material is selected to have the appropriate physicalcharacteristics for specific utilities such as tensile strength, Young'smodulus, typically 1×103 to 1×106, electroconductivity, typically 108 to1011 ohm cm volume resistivity, thermal conductivity, stability, flexstrength and in certain applications, such as transfix, being capable ofbeing subjected to high temperatures. Other important characteristics ofthe belt material include surface energy desired low for good tonerrelease, for example, gloss, dielectric constant and strength.

The puzzle cut pattern may be formed according to any conventionalshaping technique, such as by die cutting or laser cutting withcommercially available lasers, such as a CO2 laser or excimer lasergenerating a beam of sufficient width and intensity that within anacceptable time will provide the desired cut. Following cutting by thelaser beam it can be deburred and cleaned by air, ultrasonics orbrushing if necessary. In addition to puzzle cut patterns formed byjoining the two ends, they may be formed on each of the ends by a maleand female punch with the belt material in between which punches out theshape. Alternatively, it could be a pattern on a wheel which rolls overthe material.

As may be observed from the drawings, the puzzle cut pattern may takevirtually any form, including that of nodes such as identical post orneck 14 and head or node 16 patterns of male 13 and female 15interlocking portions as illustrated in FIG. 2, or a more mushroom likeshaped pattern having male portions 18 and 19 and female portions 21 and23 as illustrated in FIG. 3 as well as a dovetail pattern as illustratedin FIG. 4. The puzzle cut pattern illustrated in FIG. 5 has a pluralityof male fingers 22 with interlocking teeth 24 and plurality of femalefingers 26 which have recesses 28 to interlock with the teeth 24 whenassembled. It is important that the interlocking elements all havecurved mating elements to reduce the stress concentration between theinterlocking elements and permit them to separate when traveling aroundcurved members such as the rolls 12 of FIG. 1. It has been found thatcurved mating elements uniformly distribute stress, while square cornerelements concentrate stress, the concentrated stress leading to possiblefailure. The mechanical bonding, strength and flexibility of the bondshould be capable of supporting a belt cycling of at least 500,000cycles and the height differential between the seamed portion and theunseamed portion on each side of the seam about 0.001 inch and the seamhave a tensile strength of at least 80% and preferably 90% of the parentbelt material strength.

The following is a discussion of the interrelationship among the variousbelt and material parameters involved in the mechanical integrity of theseam. The mechanical integrity of the seam was examined and analyzed fora number of configurations and in particular for the preferredconfiguration which involves nodes forming parts of a circle andinterconnecting via a neck on the opposite side. To determine thedeflection under loading conditions, each such node is treated as a beamfixed at the narrowest part of the neck joining the node to the base andthe deflection of each tooth (node and neck) is calculated in terms ofthe orientation of the load relative to the beam. To assure that theseam will not come apart under load, it is imposed that the maximumdeflection of each tooth, when the load, under worse conditions, isnormal to the beam, would not exceed the thickness of the belt itself.Clearly, if the deflection of the tooth is in excess of the thickness ofthe belt then the seam will come apart. Under the above brief analysis,a master relationship connecting a material parameter M typical of theconfiguration with a geometric parameter G such that the belt will notcome apart under loading. $\begin{matrix}{M = \frac{1 - G}{\left( {1 + \sqrt{4 - \frac{1}{G^{2}}}} \right)^{3}}} & (1)\end{matrix}$

In this relationship M is a dimensionless quantity given by$\begin{matrix}{M = \frac{4{NR}^{3}}{{Et}^{4}}} & (2)\end{matrix}$

and G represents the ratio $\begin{matrix}{G = \frac{2R}{w}} & (3)\end{matrix}$

where N is the total load per unit width (i.e. lbs/in.) acting on thebelt, E is the modulus of elasticity of the belt material, t thethickness of the belt, R the radius of-the circular node forming theseam, and w is the wave length of one whole period between two adjacentnodes. Equation (1) is a one-to-one relationship between the materialparameter M and the geometric parameter G. Thus, given one of them wecan find the other parameter. Furthermore, because of the dimensionlessnature of these two parameters, a multitude of configurations areembodied in each pair of values satisfying equation (1), by virtue ofthe fact that there is an infinite number of combinations of thevariables involved in that particular pair of values of M and G.Inspection of the geometry of the node shows that the structure ischaracterized by two main features: the shoulder, or that portion wherethere is interference between adjacent teeth, which supports the seam,and the neck of each tooth which represents its strength under loading.The size of the shoulder should be sufficient to insure mechanicalintegrity of the seam without making the neck too small as to weaken itsstrength. In this regard attention is directed to FIGS. 6A, 6B and 6Cwherein it can be visually observed that the size of the neck in FIG. 6Ais too small and the size of the shoulder in FIG. 6C does not providesufficient interference contact while the geometry in FIG. 6B appears tobe optimum. Table 1 below lists the various parameters for theidentified belt characteristics. While all samples will function asnoted above, a value of G of 0.6 is a good compromise. Many of thesamples of course are impractical to implement relative to factors suchas manufacturing ease, costs, stress tolerance, etc. Equation (3) showsthat G can only vary between ½ and 1, the first value refers to the casewhen the shoulder is zero, and the second value pertains to the casewhen the neck of the tooth is zero and the node has no strength. Onceeither M or G is known the entire configuration becomes determinate withthe help of the above equations and other standard geometricrelationships. Measurements on actual belts have generally confirmed theabove analysis. To illustrate the solution methodology, suppose a beltmaterial of Young's modulus E=5×105 psi and thickness t=0.004″ issubjected to a tension N=2.0 lb./in. of belt width. H is theperpendicular height between centers of one node or one side of the seamand a node on the other side of the seam. The solution possibilities aregiven in Table 1 below such that the seam will not come apart. If avalue G=0.6 is chosen as a compromise between seam integrity and nodestrength, we find

Node Diameter D = 0.448 mm Period w = 0.747 mm Neck Width g = 0.299 mmNode Height H = 0.69696 G 1/M D W g H .5000 2.000 1.0160 2.0320 1.01601.0160 .5100 5.5296 .7239 1.4194 .6955 .8665 .5200 7.7482 .6469 1.2440.5971 .8246 .5300 9.7913 .5984 1.1290 .5306 .7968 .5400 11.7592 .56291.0424 .4795 .7755 .5500 13.6903 .5351 .9729 .4378 .7580 .5600 15.6054.5122 .9147 .4025 .7429 .5700 17.5179 .4929 .8647 .3718 .7295 .580019.4383 .4761 .8208 .3448 .7174 .5900 21.3751 .4612 .7818 .3205 .7061.6000 23.3363 .4479 .7466 .2986 .6956 .6100 25.3292 .4359 .7146 .2787.6856 .6200 27.3614 .4248 .6852 .2604 .6760 .6300 29.4406 .4146 .6580.2435 .6668 .6400 31.5747 .4050 .6328 .2278 .6578 .6500 33.7722 .3960.6093 .2132 .6491 .6600 36.0424 .3875 .5872 .1996 .6405 .6700 38.3950.3794 .5663 .1869 .6320 .6800 40.8411 .3717 .5466 .1749 .6236 .690043.3927 .3643 .5279 .1637 .6153 .7000 46.0632 .3571 .5101 .1530 .6070.7100 48.8678 .3501 .4931 .1430 .5987 .7200 51.8235 .3433 .4769 .1335.5904 .7300 54.9497 .3367 .4612 .1245 .5820 .7400 58.2687 .3302 .4462.1160 .5736 .7500 61.8060 .3238 .4317 .1079 .5651 .7600 65.5913 .3174.4176 .1002 .5565 .7700 69.6594 .3111 .4040 .0929 .5477 .7800 74.0510.3048 .3908 .0860 .5388 .7900 78.8149 .2986 .3779 .0794 .5297 .800084.0090 .2923 .3653 .0731 .5204 .8100 89.7035 .2860 .3530 .0671 .5109.8200 95.9840 .2796 .3410 .0614 .5012 .8300 102.9563 .2731 .3291 .0559.4911 .8400 110.7522 .2666 .3173 .0508 .4807 .8500 119.5388 .2599 .3057.0459 .4700 .8600 129.5306 .2530 .2942 .0412 .4588 .8700 141.0081 .2459.2827 .0367 .4472 .8800 154.3451 .2386 .2712 .0325 .4350 .8900 170.0512.2311 .2596 .0286 .4222 .9000 188.8397 .2231 .2479 .0248 .4086 .9100211.7410 .2148 .2360 .0212 .3942 .9200 240.2999 .2059 .2238 .0179 .3787.9300 276.9445 .1964 .2112 .0148 .3620 .9400 325.7211 .1860 .1979 .0119.3436 .9500 393.9129 .1746 .1838 .0092 .3231 .9600 496.0860 .1617 .1684.0067 .2997 .9700 666.2290 .1466 .1511 .0045 .2722 .9800 1006.3020 .1277.1303 .0026 .2376 .9900 2026.1140 .1012 .1022 .0010 .1885

N, lb/in=2.0

E, psi=500000

t, in=0.004

To minimize any time out or nonfunctional area of the belt it isdesirable to have the seam width be as narrow as possible. Further, thisenables the seam to be indexed so that it does not participate in beltfunctionality such as the formation and transfer of a toner or developerimage. Typically, the seam is from about 1 mm to about 3 mm wide.

With reference to the embodiment illustrated in FIG. 2, the seam may betypically of the order of one inch wide on a belt which is 16 to 18inches long depending on roll diameter, material modulus or otherparameters and the post and head pattern may be formed from amale/female punch cut with each end being cut separately andsubsequently being joined to form the seam with a roller similar to thatused as a wall paper seamer rolled over the seam by hand to complete theinterlocking nature of the puzzle cut pattern.

The two ends of the belt material are joined by physically placing themtogether in interlocking relationship. This may require the applicationof pressure to properly seat or mate the interlocking elements. Theadhesive material may be the same or it may be different from thematerial from which the belt was fabricated and may be selected fromthose materials previously discussed. Typically, it is a heat sensitivethermoplastic or thermoset material. It may be either chemically, and/orphysically bound to the belt material. The chemical and/or physical bondbetween the adhesive and the belt material may also be formed by theapplication of heat and/or pressure after the adhesive has been appliedIn a particular application impulse welding may be applied wherein heatand pressure are simultaneously applied to at least soften the beltmaterial and the compatible adhesive material 17 (see FIG. 7) so that itfills the kerf and forms an adhesive bond with the belt material. Inthis regard, it is important that the heat applied does not exceed thatwhich would both form the seam and break it by melting it or decomposingit. Other heat sources include conventional heated rolls, a simpleheated iron, ultrasonic welding or a two roll heated nip providing acombination of heat and pressure.

Preferably, the adhesive material applied is of a thickness to provide aquantity of adhesive to fill the kerf spaces between the two sides ofthe puzzle cut seam member. In this regard it should also be noted thatit may be possible to first apply the heat to, the seam of the beltmaterial and the adhesive and subsequently apply pressure while it isstill in a softened condition to force the softened adhesive into kerfor the spaces between the two sides of the puzzle cut seam members. Thepressure applied should be sufficient to fill the kerf and to minimizethe thickness of any bonded joint. While this process clearly provides aphysical bonding between material of the belt seam and the adhesivematerial, it may also provide a chemical bond. A typical example of thiswould be one wherein the belt material is a polyimide and the adhesiveis a polyimide.

Following fabrication, the belt may be finished by way of buffing orsanding and further, may have an overcoating applied, typically, of athickness of 0.001 to 0.003 inch in thickness which can be initiallyapplied to the unseamed belt, the belt seam and the seamed area filledfrom the back of the belt to maintain the uniformity of the functionalsurface. Preferably, and by far the most economical matter is to formthe belt seam initially and then apply the desired overcoating.

The seamed belt according to the present invention may be fabricated inan environmentally acceptable manner in that no solvents are required.The adhesive may be applied to the belt in a suitable manner, such as bybeing applied from a tubular applicator by squeezing or pushing or beingapplied by a spatula. It may be applied on one or both sides of the kerfor voided area and is preferably smoothed on it's surface to provide asmooth surface in the seam area of the belt.

EXAMPLE 1

Using a die cutter, a one inch wide polyimide material was mechanicallycut to provide a radius of the nodes of about 0.5 mm and the center tocenter spacing of about 0.70 mm. The ends of the strip of the one inchwidth polyimide material were then interlocked and rolled with theroller to flatten the seam. A thermoplastic polyamide web material wasplaced on the lower jaw of an impulse welder Vertrod Corp. Model No.24H/HT1/4. The previously joined seam was then centered over the webbingmaterial, heat at approximately 350° F. and light pressure were thenapplied to melt the polyamide web material into the seamed area forapproximately 20 seconds. With the seam remaining on the lower jaw ofthe impulse welder, both sides of the seam were then masked withconventional masking tape, a bead of a polyimide adhesive was squeegeedinto the area formed by the masking tape and permitted to flash torelease solvent for about 15 minutes after which the masking is removed.The impulse welder is once again clamped again and the seam receives twocycles of 350° F. heat for 35 seconds. The seam remained in the impulsewelder for 30 seconds before it was removed and postcured at 400° F. for2 hours and then room temperature dwell for at least 12 hours. Fourteen,12 inch long belts were tested in the flex tester and all had flexingcycles exceeding 750,000 with 9 samples exceeding one million cycles. Ofthe nine belts, which flexed for over a million cycles, the test wasdiscontinued without any of the belts failing. The samples were testedin a flex tester using two pounds in loading, 17 inch per second processspeed around the 25 mm drum rollers.

Turning now to FIG. 10, which shows a front view of the die pressassembly used to cut the patterned ends of the belt. Die 102 issupported by die retainer plate 106. Punch 104 is supported over the die102 by punch retainer plate 108 and punch assembly retainer 120. Astripper 114 surrounds the punch 104, there being a very small clearancebetween the punch and stripper. Stripper 114 has a puzzle cut patternwhich is complementary with the punch puzzle cut pattern so that thestripper assists in locating the punch with respect to the die. Thestripper is fixed to die 102 so that a stock gap exists for the beltmaterial 111 to pass between the stripper and die. The stock gap isformed by shims 142 (see FIG. 11) between the stripper and the die. Thestripper 114, die 102 and die retainer plate 106 are fixed together andremain stationary during the belt cutting process.

Timing blocks 112 are mounted to both ends of punch retaining plate 108and are located above stripper 114. Timing blocks 112 cooperate to keepthe punch assembly level; when the first timing block hits stripper 114this causes the punch assembly to level out and when the other timingblock hits the stripper, the direction of punch assembly is reversed(discussed below).

Guide posts 116 pass through punch retainer plate 108 and die retainer106 and assist in keeping all of the punch and die members properlyaligned. Punch return assembly 118 connects the punch retainer plate 108and die retainer 106 and returns the punch to its ready to cut positiononce the cutting force is removed. Punch assembly retainer 120 supportspunch retainer plate 108, punch 104 and timing blocks 112; punchassembly retainer 120, punch plate 108, timing blocks 112 and punch 104being fixed with respect to each other. Punch assembly retainer 120 is asolid piece of metal and distributes the cutting force along the fulllength of punch retaining plate 108.

At the top center of the punch assembly retainer is force receivingsurface 122. Above force receiving surface 122 is force generatingassembly 124 having a force generating surface 126, a cylinder travelgap 128 being formed between the two surfaces when the force generatingassembly is in the retracted position The force generating assembly maybe a hydraulic press or any equivalent press which can generatesufficient force to cut the belt material. Force generating assembly 124provides a downward force with force generating surface 124 contactingforce receiving surface 122 which supplies the cutting force to thepunch assembly until both timing blocks 112 contact stripper 114 (asshown). At this time the force generating assembly force direction isreversed and the cutting force removed. Punch assembly 120 moves upwarddue to the upward force of spring 121 of punch return assembly 118, thetop of the bolt 119 limiting the upward movement of the punch.

Force generating assembly 124 is supported independently of the punchand die members. Force generating assembly horizontal support 130 andvertical supports 132 are attached to die table 140. Vertical supports132 have a foot member 134. Die retainer 106 supports all of the punchmembers and die members and is also attached to die table 140. As shown,die retainer 106 has cut out portions 136 on its underside with footmembers 134 captured in the cut out portions. This configuration ensuresthat force generator assembly horizontal support 140 will remainstationary with respect to the die when the cuffing force is supplied byforce generating assembly 124.

Rather than having the punch assembly attached to the force generatingmember as is usual for die presses, the punch members are fixed to thedie members by punch return assembly 118. The punch return assembly 118shown has a plurality of punch return assembly bolts 119 and punchreturn assembly springs 121, which connect the punch and die assembliesand bias the punch assembly towards the force generating assembly, awayfrom the die assembly, when the cuffing force is removed. Thisconfiguration allows the punch and die to remain in close proximity andproperly aligned with one another. Any misalignment of the punch and diewould result in catastrophic failure when the next punch force isapplied.

An exploded view of the punch and die assemblies is shown in FIG. 11.The cutting assembly 100 is formed of a die 102 and punch 104. The dieand punch have complementary surfaces which form the puzzle cut patternwhen the cutting operation is performed. Die 102 has two die cuttingedges 160 and 161 and punch 104 has two punch cutting edges 162 andanother edge (not shown). Die cutting edge 160 and punch cutting edge162 interact to form the puzzle cut pattern at the first end of a beltand die cutting edge 161 and the other punch cutting edge interact toform a complementary puzzle cut pattern for the second end of a belt.There is a very small clearance between punch cutting edges and the diecuffing edges to ensure proper cutting tolerances of belt material 111.A stock gap is formed between stripper 114 and die 102 surfaces withshims 142 spacing the two members for the desired stock gap width.

Stripper 114 holds the cut belt material in place as the punch returnsto its pre-cut position, thus performing its stripping function. Inoperation, the die assembly cuts the second end of one belt at the sametime it cuts the first end of another belt. This process results inwaste material the width of the die and punch. The belt material is fedthrough the stock gap in any known manner, for example as a mechanizedor hand placement process, the length of the belt being determined bythe amount of belt material fed between cutting operations.

The first feature that required development in forming the extremelyaccurate punch and die cutting edges was the proper steel and heattreatment process to maintain less than 0.04% dimensional change and nowarpage when wire cut or ground. After several experiments, the optimummaterial and process was D-2 steel, 0.5 inch thick die plates hardenedto R/C 57 and drawn three times at 1875 Fahrenheit. After hardening, theplates were cryogenically treated to −120 Fahrenheit. Then two more drawoperations at 920F and 950F were performed. A cut relief 104 wasincorporated in the center of the die to relieve stress prior tohardening. The treated material was then cut using an EDM technique, thepunch 102 and die 104 plates being formed separately. Four cuttingpasses were required to maintain tolerances so that the very small nodesand even smaller spacing tolerances required were produced in thefinished punch and die. The last cutting pass was a skimming pass of0.0002 inches. The length of the die depends upon the desired beltwidth. The belt width can be as much as 60 inches using the drawing andEDM cuffing techniques outlined above.

EXAMPLE 2

The particular configuration of the puzzle cut with the rounded puzzlecut pattern will be discussed (see FIGS. 8 and 9), however any desiredpattern could be formed with the appropriate punch and die pattern. Theapproximate clearance between the punch and die patterned edges was0.0002 inches, the punch and stripper clearance was 0.0001 inches, theclearances being measured on each side of the punch and die. The nodediameter was 0.5 mm and the kerf dimension was 25 microns. The punchassembly is returned approximately 0.100 inches above the belt materialafter the cut is made. The punch and die cutting edges were configuredso that the seam is at a slight skew with respect to a 90 degreestraight edge belt, which increases the integrity of the seam. The beltmaterial used was Mylar and the width of the belt cut was 18 inches.Different sizes of belts could be cut with one edge of the belt beingaligned with one side of the punch/die assembly to insure that the nodesare properly aligned. Using the above shapes, tolerances and materials,a “seamless”, i.e. a belt which essentially performs as a seamless belt,puzzlecut transfer belt was produced.

The above cross referenced patent applications together with the patentscited herein are hereby incorporated by reference in their entirety inthe instant application. It is, therefore, apparent that there has beenprovided in accordance with the present invention, a precision punch anddie and a die press for forming puzzle cut patterned belts that fullysatisfies the aims and advantages hereinbefore set forth. While thisinvention has been described in conjunction with a specific embodimentthereof, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art. Accordingly, itis intended to embrace all such alternatives, modifications andvariations that fall within the spirit and broad scope of the appendedclaims.

We claim:
 1. An apparatus for producing an endless flexible seamed beltfrom belt material stock, comprising: a die assembly including a diewith a first die cutting edge having a first puzzle cut die patternhaving a series of alternating nodes with diameters from about 0.1 mm toabout 1.0 mm, wherein the nodes of the first puzzle cut die pattern forma body portion and a neck portion such that the width of the bodyportion is larger than the width of the neck portion, and a second diecutting edge opposite the first die cutting edge having a second puzzlecut die pattern having a series of alternating nodes with diameters fromabout 0.1 mm to about 1.0 mm, wherein the nodes of the second puzzle cutdie pattern form a body portion and a neck portion such that the widthof the body portion is larger than the width of the neck portion; apunch assembly including a punch with a first punch cutting edge havinga first puzzle cut punch pattern that is complementary to the firstpuzzle cut die pattern and a second punch cutting edge opposite thefirst punch cutting edge having a second puzzle cut pattern that iscomplementary to the second die puzzle cut die pattern; and a forcegenerating assembly which generates a cutting force in a cuttingoperation in which the punch and the die cut the belt material stocksuch that a first puzzle cut patterned end is formed on a first end ofthe belt material stock, and a second puzzle cut patterned end is formedon a second end of the belt material stock, such that the first andsecond puzzle cut patterned ends are able to mate to form an endlessbelt.
 2. An apparatus as claimed in claim 1, the force generatingassembly further comprising: a horizontal and two vertical supports,each of the vertical supports having a foot member which fits under thedie assembly enabling the horizontal support to remain stationary duringthe cutting operation.
 3. An apparatus as claimed in claim 1, wherein afirst end of one belt and the second end of another belt are cut in thesame cutting operation.
 4. An apparatus as claimed in claim 1, whereinthe belt material stock has a thickness of about 0.004 inches.
 5. Anapparatus as claimed in claim 1, further comprising: a force generatorsurface on the force generating assembly that transmits the force of theforce generating assembly to the punch assembly; a force receivingsurface on the punch assembly for receiving the force of the forcegenerating assembly; and a gap formed between the force generatorsurface and the force receiving surface when the force generatingassembly is in a retracted position so that the punch assembly isdisconnected from the force generating assembly after each cuttingoperation.
 6. An apparatus as claimed in claim 5, further comprising: apunch return assembly having at least two bolts connecting the die andthe punch assemblies together; and at least two springs, one springmounted on each bolt, the springs biasing the punch towards the forcegenerator surface and the bolts limiting the movement of the punch in adirection towards the force generator surface to about 0.05 inches to0.2 inches when the cutting force is removed.
 7. An apparatus as claimedin claim 1, further comprising: a stripper member through which thepunch passes when the cutting force is applied by the force generatingassembly, the stripper member having a first stripper puzzle cut patternwhich is complementary to the first puzzle cut punch pattern and asecond stripper puzzle cut pattern which is complementary to the secondpuzzle cut punch pattern, the stripper member stripping the cut beltmaterial stock from the punch.
 8. An apparatus as claimed in claim 7,further comprising: a belt material stock gap formed between thestripper member and the die, the belt material stock gap being fromabout 0.05 to 0.2 inches.